The effects of soil depth on annual grasses in the judean hills. I: The effect of soil depth on individual plant species

Four different annual grasses, which are distributed along a soil depth gradient in rocky upland habitats of the Judean Hills, were chosen for pot experiments in order to study the factors and processes determining their distribution. Soil depth strongly affected plant phenology and several parameters of plant productivity, all of which increased with increasing soil depth. In the absence of competition, species normally dominating in shallow soils (such as Bromus fasciculatus Presl. and Brachypodium distachium Roem. et. Schult.) grow as well or even better when sown in deeper soils. Thus it is assumed that the low coverage of these small species in deep soils is due to competition with tall species such as A vena sterilis L. or Hordeum sponlaneum C. Koch, which are more efficient in utilizing available resources under more favourable conditions. Hordeum sponlaneum grew very poorly in the shallowest soil. In contrast, all the other species have a wide ecological range of survival, which enables them — in the absence of specific competition — to complete their life cycle in all soil depths. In addition, they are apparently better adapted to the shallow and poor soils which are abundant in the Judean Hills.